Re: [RFC PATCH 4/9] iommu/rockchip: skip orphaned-fault banks in rk_iommu_is_stall_active

[Chaoyi Chen]

Hello Jiaxing, 

On 7/17/2026 4:50 PM, Jiaxing Hu wrote:
> Boot firmware can leave a PAGE_FAULT_ACTIVE condition in an IOMMU bank
> before the driver has configured paging.  Such a bank shows:
> 

I'm not sure what's happening here. Does this issue still occur when
you reset the MMU?

>   PAGE_FAULT_ACTIVE=1  STALL_ACTIVE=0  IDLE=1
> 
> rk_iommu_is_stall_active() sees STALL_ACTIVE=0 and reports the whole
> IOMMU as "not stalled", so any subsequent readx_poll_timeout() loop
> waiting for the stall to complete never sees a passing result even
> after the other banks have correctly entered stall mode.
> 
> Detect the orphaned-fault pattern (PAGE_FAULT_ACTIVE & !STALL_ACTIVE &
> IDLE) and skip those banks in the stall check.  They have no in-flight
> transaction, so they are already quiescent.
> 
> Signed-off-by: Jiaxing Hu <gahing@xxxxxxxxxxxxx>
> ---
>  drivers/iommu/rockchip-iommu.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
> index 0013cf196..f42ffcafb 100644
> --- a/drivers/iommu/rockchip-iommu.c
> +++ b/drivers/iommu/rockchip-iommu.c
> @@ -378,9 +378,23 @@ static bool rk_iommu_is_stall_active(struct rk_iommu *iommu)
>  	bool active = true;
>  	int i;
>  
> -	for (i = 0; i < iommu->num_mmu; i++)
> -		active &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> -					   RK_MMU_STATUS_STALL_ACTIVE);
> +	for (i = 0; i < iommu->num_mmu; i++) {
> +		u32 status = rk_iommu_read(iommu->bases[i], RK_MMU_STATUS);
> +
> +		/*
> +		 * A bank stuck with PAGE_FAULT_ACTIVE but without STALL_ACTIVE
> +		 * and with IDLE set has an orphaned fault left by firmware before
> +		 * paging was configured.  It cannot enter stall mode but has no
> +		 * transaction in flight, so it is already quiescent.  Skip it
> +		 * rather than treating it as "not stalled."
> +		 */
> +		if ((status & RK_MMU_STATUS_PAGE_FAULT_ACTIVE) &&
> +		    !(status & RK_MMU_STATUS_STALL_ACTIVE) &&
> +		    (status & RK_MMU_STATUS_IDLE))
> +			continue;
> +
> +		active &= !!(status & RK_MMU_STATUS_STALL_ACTIVE);
> +	}
>  
>  	return active;
>  }

-- 
Best, 
Chaoyi